The present invention relates generally to piping used in various industries to move fluid; and more particularly to a system for mitigating flow-induced vibrations (FIV) associated with transport and/or circulating a cooling fluid in heat-generating systems, such as nuclear reactors and hydroelectric generation systems.
Structural conduits, such as, but not limiting of, pipes, tubes, and cylinders are commonly used to transport a variety of fluids. Typically, the conduits are submerged in the same fluids that the conduit is transporting. For example, but not limiting of, the tubular components of a jet pump assembly are housed within a nuclear reactor pressure vessel (RPV) and reside in the fluid that the jet pump transports. Here, the jet pump assembly transports the cooling water to the reactor core, while the jet pump assembly is submerged in the same cooling fluid.
The conduits that comprise such submerged systems are typically supported within the surrounding structures (e.g., the RPV) by a restraining apparatus. The surrounding structures may be formed of a material different than the conduit material. For example, but not limiting of, the RPV may be formed of carbon steel; and the jet pump assembly may be formed of stainless steel. These different materials tend to have different thermal coefficients of expansion. In order to accommodate for the different amounts of thermal expansion associated with RPV operation, slip joints are installed along the conduits to minimize thermal stress within the conduits.
Experience has shown that if a sufficient pressure gradient exists across slip joint interfaces, the connecting tubular components may incur detrimental FIV. This may lead to a failure possibly resulting from excessive wear and/or fatigue of the conduit material or the support/restraining apparatus. These failures may occur to the jet pump assemblies used in RPVs.
The slip joint typically has an operating clearance that accommodates the relative axial thermal expansion movement between components of the jet pump assembly. This clearance permits a leakage flow from the driving pressure inside the jet pump assembly. Excessive leakage flow, however, can cause an oscillatory motion in the slip joint, which may be one source of FIV experienced by the jet pump assembly.
Some known systems and methods for mitigating this FIV may be insufficient in producing a long-term and effective reduction of the vibration. In addition, those systems and methods may impose a lateral force on the slip joint. This lateral force may prevent axial movement in the slip joint, and not properly allow for adequate thermal expansion in the slip joint.
Based on the above discussion, there may be a desire for a system for reducing the FIVs experienced by a conduit submerged within the fluid that the conduit transports. The system should provide a simplified way to prevent and/or mitigate the FIVs.